Grinding machine



Nov. 17, 1964 G. H. LOCKWOOD GRINDING MACHINE 2 Sheets-Sheet 1 Filed Dec. 20, 1962 Nov 17, 1964 G. H. LOCKWOOD GRINDING MACHINE 2 Sheets-Sheet 2 Filed Dec. 20, 1962 INVENTOR. Cjeorqe H. .Cocllurooal BY 3% /."1 -/I l H 'rney United States Patent 3,157,t307 GRZNDTNG MACHDYE George H. Lockwood, Worcester, Mass, assignor to The Heaid Machine Company, Worcester, Mass, at corporation of Deliaware Filed Dec. 2%, 1%2, Ser. No. 246,164 3: Ciaims. (Cl. 51-4165) This invention relates'tto a grinding machine and, more particularly, to apparatus arranged to generate an internal surface of revolution by the abrasion method.

In the grinding of internal surfaces of revolution, it is common practice to regulate the various phases of the grinding cycle by means of a gauge which measures the surface as the process progresses. It is particularly advantageous to measure the surface continuously while the abrasion process takes place. However, as is well known, it is desirable that the abrasive wheel occupy a large percentage of the area of the bore in the workpiece as is possible, so that very little space remains between the wheel and the surface of the bore for the insertion of a gauge. Such gauges that have been developed in the past have suffered from a number of deficiencies all of which affect the accuracy of gauging. For instance, in many workpieces the tolerance on the dimension of the outside diameter of the workpiece is relatively large compared to the desired tolerance on the inner bore. When the workpiece is supported on its outer surface variations in the outside diameter tend to affect the relationships in the bore and make it difncult to obtain accuracy. Furthermore: since the gauge is connected to the shoe support through considerable amounts of intervening metal, a thermal loop is formed which expands and contracts with the machine temperature, so that the relationship between the gauge and the rest of the machine changes and produces inaccuracies in gauging. When the internal surface is a groove or the surface to be gauged is behind a shoulder, it is very difiicult to insert a gauge; the use of intricate slides and similar mechanism introduces backlash and looseness into the gauging system which also results in inaccuracy. These and other difiiculties experienced in connection with the prior art devices have been obviated in a novel manner.

It is, therefore, an outstanding object of the invention to provide a grinding machinerfor producing internal surfaces of revolution having an arrangement for gauging which gives accurate results irrespective of variations in the outer diameter of the workpiece.

An important object of the present invention is the provision of a grinding machine having gauging apparatus capable of measuring a surface of revolution.

Another object of this invention is the provision of a grinding machine having a gauging apparatus in which inaccuracies due to thermal expansion and contraction are minimized.

It is another object of the instant invention to provide 3,157,067 Patented Nov. 17, 1964 the combination of parts set forth in the specification and covered by the claims appended hereto.

The character of the invention, however, may be best understood by one of its structural forms as illustrated by the accompanying drawings in which:

FIG. 1 is an elevational view of a portion of a grinding machine embodying the principles of the present invention taken on the line II of FIG. 2; and

FIG. 2 is a sectional view of the apparatus taken on the line II-Il of HG. l.

The grinding machine, indicated generally by the reference numeral it), is shown in operation forming an internal surface of revolution 11 in a workpiece 12. The surface of revolution 11 includes a groove 13 which, for the purpose of illustration, is the surface to be ground; the illustrated workpiece is, therefore, similar to the outer race of a ball bearing.

The grinding machine it is provided with a base 14 on which is mounted a Wheelhead 15 carrying a spindle 16 which is provided at its outer end with an abrasive Wheel 17. The abrasive Wheel is dressed with an annular surface, as is usual practice in the grinding of grooves. The wheelhead 15, of course, rotates the spindle 16 at high speed in the Well-known manner. The grinding machine 10 is of the general type shown and described in the patent application of Hohler et al., Serial Number 217,683, filed August 17, 1962.

Also mounted on the base 14 of the grinding machine is a workhead 18 carrying a support 19 and a magnetic drive spindle 21 which is rotatably engaged with one end of the workpiece I2 and serves to drive it. For purposes of illustration, the drive spindle 21 is not shown in FIG. 1. The support 19 is provided with a reduced porticn 20 carrying hardened metal shoes 23 and 24 which, in the preferred embodiment, are formed of tungsten carbide. These shoes extend inwardly of a cylindrical surface of the reduced portion 20. The shoe 24 lies directly under the workpiece and is provided with a surface to contact the cylindrical outside diameter of the workpiece 12. The shoe 23 is located away from the shoe 24, both shoes being provided with surfaces which contact the workpiece and which are 90 apart, so that, in

effect, the workpiece is supported in a 90 V. The surfaces of the shoes may be perfectly flat or may have a curvature to fit the outside surface; in this discussion, the surfaces will be treated as though they were flat.

The support 19 is formed with a milled slot 25. Pivotaily mounted in this slot is a supporting member 26. A bore 27 extends through the support 19, the axis of the bore extending at an angle of 45 to the vertical, as is evident in FIG. 1; the axis also lies in a vertical plane which extends through the center of the groove 13 in the workpiece which is the point in the surface to be finished which will be subject to gauging. A shaft 28 extends through the supporting member 26 and is locked therein by a set screw 29. The shaft fits for rotation in the bore 27 and is provided at its ends with conical surfaced sockets 31 and 32. A comically-pointed pivot member 33 is locked in the bore 27 with its conical point fitting tightly into the socket 31. A similar pivot member 34- fits in the upper part of the bore 27 and engages the socket 32. The supporting member 26 has a portion which normally extends forwardly of the front surface of the support 19, and on this is mounted a gauging apparatus 35. The gauging apparatus has a downwardly extending flange 36 i e which is bolted to the supporting member 26 and has a main body 37 terminating in a finger 33. The gauging apparatus is connected by a flexible conduit 39 to a conventional air regulating apparatus of a grinding machine, which apparatus controls the grinding cycle in the manner shown and described in the patent of Schmidt et al., No. 2,771,714, which issued November 27, 1956. An air passage 41 extends through the main body 37 of the gauging apparatus and through the finger 38 and opens in a nozzle 42 located'at the extremity of the finger 33 and is located in the deepest part of the groove 13 and also in the transverse plane which includes the axis of the bore 27 and the pivot shaft 28 of the gauging apparatus.

The outer end of the supporting member 26 is provided with an elongated tailpiece 43 whose outer end is com nected by a flexible metal reed 44 to a linear actuator, such as a hydraulic cylinder 45 mounted on the support 19. The reed is connected to a piston rod 46 whose other end is provided with a piston 47 which is slidable in a cylinder 48. The cylinder is provided with an upwardly-directed flange 49 (see FIG. 1) which is bolted to a vertical longitudinal surface of the support 19. One end of the cylinder 48 is connected to a conduit 51, while the other end of the cylinder is connected to a conduit 52, these conduits being connected for automatic operation of the cylinder. The tail piece 43 is provided with an elongated extension 53 which moves with it and is adapted on occasion to engage a limit switch 54. The limit switch is connected into the electrical portion of the grinding machine in such a way as to act as an interlock to assure that the unloading of the workpiece does no take place 'until the gauging means is entirely removed from the bore of the workpiece.

The operation of the apparatus will now be readily understood in view of the above description. The grinding machine operates on the workpiece in the usual way, the drive shaft 21 rotating the workpiece 12, and serving to resist axial thrust. The usual control means of the machine will move the wheel 17 into place in the bore of the machine and then advance it laterally into the groove 13 to grind and finish the surface thereof. The gauging apparatus 35 is placed in operative position by the introduction of oil pressure in the conduit 51 and the connection of the conduit 52 to drain. This causes the piston 47 to move to the right (in FIG. 2) and causes the supporting member 26 to pivot in a counterclockwise manner about the axis of the bore 27. This will cause a corresponding counter-clockwise movement of the main body 37 of the gauging means and causes the finger 38 with the nozzle 42 to move in an arcuate manner into the bore of theworkpiece. This arcuate movement of the protuberance presented by the nozzle 42 causes it to clear the shoulder of the workpiece bore and to move into the deepest part of the groove 13. When the cylinder 47 reaches the extreme end of the cylinder 48 it comes to a positive stop again-st the head of the cylinder and this locks the gauge in place. At that time, the nozzle is located in the groove 13 and the opening of the nozzle from which the air passes is located a short distance from the surface, so that it gauges very accurately the position of the surface of the groove relative to the axis of the workpiece and, thus, the diameter of the surface of revolution. The escape of air through the annular space between the nozzle lip and the surface of the groove 13 makes itself felt through the air passage 35 and the con duit 39 to the control apparatus of the grinding machine. As the groove 13 becomes deeper and approaches the finish size, the escape of air will be greater until, eventually, the groovereaches its finish size, at which time the grinding cycle is terminated. The changes from rough 1 grind to finish grind, and so on, take place in the wellknown manner. When the grinding cycle is finished,

positive oil is presented in the conduit 52 and the conduit 51 is connected to drain sothat the piston 47 moves to the left inthe cylinder 48. This carries the gauging means out of the bore and clear of the workpiece, as shown in the dotted line representation of the elements. When the piston 47 reaches its extreme position against the inner head of the cylinder, the extension 53 engages the actuating member of the limit switch 54 and thus, through the interlock, permits the removal of the workpiece and the insertion'of a new workpiece in place.

As is evident in FIG. 1, the nozzle 42 lies opposite the portion of the workpiece being gauged on a line which, when joined to the axis of the bore in the workpiece, is at a right angle to a bisector of the planes of the contact surfaces of the shoes 23 and 24. 'In other words, the shoes 23 and 24 present a 90 V and an imaginary line bisecting the V passes through the center of the workpiece. it the shoe surfaces are curved, then the bisector would be related to planes tangent to the surfaces at their center points. in any case, the nozzle lies on a line which is at a right angle to this bisector and which passes adjacent to or exactly on the center of the axis of the workpiece. The effect of this arrangement is that, with changes of outside diameter of the workpiece 12, the workpiece will sit higher or lower in the V, so that the nozzle 42 will lie opposite sligitly different portions of successive workpieces. However, because of the geometric relationship, the nozzle is moved along the arc of the surface being ground and it affects very little the gauging of successive work pieces. In this way, although the outside diameters of successive workpieces may vary by considerable amounts, this will not affect the gauge setting and very accurate work will be accomplished. Furthermore, the effect of thermal expansion and contraction in the machine will have little effect on the gauging because the thermal loop passes from the workpiece,

through the shoes 23 and 24, through a short portion of the support 1), into the pivot shaft 28 and the supporting member 26, through the flange 36 of the gauging apparatus, through the finger of the gauge to the workpiece surface. Therefore, this loop is dimensionally very small and thermal changes in the machine will affect the gauging to a negligibleextent. It can be seen that the use of the inclined pivot defined by the axis of the bore 27 permits the insertion of the finger over a raised portion of the workpiece into a groove or a portion of a bore beyond. a shoulder. This is because the nozzle 42 moves in an arc. in moving in and out of gauging position and by properly selecting the distance from the surface to be gauged and the pivot bore 27, the arc can be made as sharp as is necessary to permit the nozzle to move over intervening raised areas in the internal bore.

t is obvious that minor changes may be made in the from the material spirit thereof. it is not, however, de-

sired to confine the invention to the exact form herein shown and described, but his desired to include all such as properly come within the scope claimed.

The invention having been thus described, what is claimed as new and desired to secure by Letters Patent, is: 1. Apparatus for use in grinding a first surface of revolution on a workpiece having another substantially concentric second surface of revolution, comprising (a) a work support consisting of two surfaces whose contact points with the second surface of revolution form with the center of the workpiece a V, and (b) a gaging means adapted to lie adjacent the first surface of revolution at a point lying on a line which extends substantially at a right angle to a bisector of the! and which passes through the center of the workpiece. V 2. Apparatus for use in grinding an internal bore in a'workpiece having an outer surface of revolution, comprising V (a) a work support consisting of two hardened metal shoes whose surfaces form a v adapted to contact the said outer surface of the workpiece, and

(b) a gaging means adapted to lie adjacent the surface of the bore at a point lying on a line which extends at a right angle to a bisection of the V and which passes adjacent the center of the workpiece.

3. Apparatus for use in grinding an internal bore in a workpiece having an outer surface of revolution, comprising (a) a work support consisting of two shoes whose surfaces form a V adapted to contact the said outer surface of the workpiece,

(b) a single air nozzle gage adapted to lie adjacent the surface of the bore at a point lying on a line which extends at a right tngle to a bisection of the V and which passes adjacent the center of the workpiece, and (c) means for moving the gage in and out of the bore.

References Cited by the Examiner UNITED STATES PATENTS 1,662,213 3/28 Steiner 33172 2,909,009 10/59 Schmidt et al 5l165.04 X 3,019,565 2/62 Hatstat et a1. 51--165.04

I. SPENCER OVERHOLSER, Primary Examiner.

LESTER M. SWINGLE, Examiner. 

1. APPARATUS FOR USE IN GRINDING A FIRST SURFACE OF REVOLUTION ON A WORKPIECE HAVING ANOTHER SUBSTATIALLY CONCENTRIC SECOND SURFACE OF REVOLUTION, COMPRISING (A) A WORK SUPPORT CONSISTING OF TWO SURFACES WHOSE CONTACT POINTS WITH THE SECOND SURFACE OF REVOLUTION FORM WITH THE CENTER OF THE WORKPIECE A V, AND (B) A GAGING MEANS ADAPTED TO LIE ADJACENT THE FIRST SURFACE OF REVOLUTION AT A POINT LYING ON A LINE WHICH 